LGB333

Member

In case folks haven't seen a pulsed smoke unit working in a DCC equipped locomotive, thought I'd share this information. I just finished installing a DCC Massoth eMotion XLS Sound Decoder and a Massoth #8415001 Pulsed Smoke Round Boiler-style Unit into an LGB Uintah that I'm working on for a customer. Some sections of the Massoth German to English translations in the Installation Manuals are not that clear so I was very frustrated getting the smoke unit to work properly. I thought I had a defective smoke unit until I contacted my Massoth dealer in Germany who gave me clear directions, and now it works like a champ! I had to build from scratch a platform to fasten the smoke unit to based upon the large cavity inside the Uintah's smoke box, and then covered it with metal duct tape to protect the glue joints from smoke fluid........see photo. I'll also try to attach a video of the Uintah and smoker operating on my roller wheels test stand.......not sure this forum's system allows videos to be posted or not. But you can view the video on my Website.

LGB333

Member

The solution was to connect the Brown wire to the decoder's A3 "pulsed" connection, and the Black wire to the decoder's DEC - ground, not the assumed DEC + connection. The A1 - A5 outputs are normally (-) so Ground would normally be (+). Who would have guessed it!

Greg - See the photo of the Massoth XLS Sound Decoder: The Massoth Instructions for the Pulsed Smoke Unit stated to connect the supplied two colored cable leads, Brown wire to the XLS decoder's A3 (- ) connection (CV114), and the Black wire to the "Ground - it would have been helpful to state whether it should be Ground + or Ground -. You also change the XLS decoder's A3 CV114 to "30" to activate the "pulse" feature from the connection. The Smoke Unit's other two Black wires are connected to the Track Power. Note that all the A1 - A4 connections on the XLS decoder are (-). So, since the Smoke Unit's Instructions didn't specify whether the Ground should be positive (DEC+) or negative (DEC-) connected, then logic told me to connect the smoker to the positive (DEC+) Ground......doesn't that make sense since, as you can see on the XLS decoder photo, the A1 - A4 connections are all 22 volts negative (-). When I did that, the smoker would work for a about 20 seconds then stop. But I was advised to connect it to the negative Ground (DEC-) and then it worked great. So, could you further explain why my assumption about using the DEC+ Ground was incorrect?

Paul M

Registered

PhilP

G Scale, 7/8th's, Electronics

To be fair (although 'lazy' terminology) is is 'not unusual' (I won't use the word 'common' ) to use the term 'ground' to refer to the 'commoned' connection for ancillary devices.

You can, of course, have a '0v' ground connection, with negative and positive supply rails relative to this 'ground potential'.

It all depends where you deem your reference point to be.. Also, it is only at 'ground potential', if it is actually 'grounded' (connected to your local ground), Otherwise it is floating with respect to local ground, and could be anything.

John S

Registered

The Positive and Negative for the Pulsed Smoke Unit, are taken from the DCC Signal/Voltage input via a bridge rectifier to supply the correct internal voltages for the Pulsed Unit to operate correctly.

Starting with the Pulsed Smoke Unit, the explanation is simple, by the very nature of changing CV 114 for the A3 OUTPUT to 30, converted this OUTPUT from voltage to a signal.

The A3 OUTPUT from the decoder supplies a pulsed signal consisting of "0's" and "1's" to the INPUT of the Pulsed Smoked Unit, and depending on whether the INPUT is zero "0" or one "1" the microprocessor within the Pulsed Smoke Unit carries out the relevant instructions written in the program code (Firmware), the microprocessor requires a reference point hence the GND (Dec-) is also connected, so a pulse of zero's LOW, referenced against GND (Dec-) LOW, do so and so, pulse of one's HIGH, referenced against GND (Dec-) LOW, do something else.

As for the rest, a picture is worth a thousand words. (Depending on the Massoth Decoder, A5 could be one of two very different definitions). As ever refer to the documentation that is supplied with the decoder, refer to the text, and any pictures or diagrams to correctly identify what defininations are used, Massoth decoders have differences across the range of various decoders.

Greg - Okay, I get it, the term Ground means use the DEC (-) terminal on the sound decoder. So, my terminology was incorrect about the DEC (+) terminal which is +22 volts. The Massoth Pulsed Smoke Unit's Installation Instructions stated to connect the black wire from the Brown/Black two wire cable to the Ground terminal on the Massoth Sound decoder. The Brown wire is then connected to the A3 (-) terminal and when its CV114 is changed to 30, it creates the pulsed output. So, contrary to my original criticism, the Smoke Unit's Instructions does not need to state connect the Black wire to "Ground DEC (-) terminal", since Ground explicitly means the DEC (-) terminal on the decoder. What confused me was the A3 terminal is (-) and connecting the other wire to DEC (-) seemed like a connection conflict (-) to (-) but it wasn't. As they say, "my bad"!

Greg Elmassian

Registered

Short translation of John's post for the mildly curious, but not wanting to become an electrical engineer:

The smoke units need pulses of voltage from 0 volts to a positive voltage The decoder does pulses, but switches it's output from sort of undefined to ground, i.e. it pulses to ground not pulses to positive voltage

The circuit with the transistor basically "inverts" the pulses so now you are applying pulses of positive voltage to the smoke unit.

This same thing happened on the Bachmann K27 locos, where the pulse from the "chuff switch" was inverted from what most sound units needed.